Electric circuit interrupter



May 25, 1937.

E. B. MERRIAM ELECTRIC CIRCUIT INTERRUPTER Filed Jan. 2s, 193s OIL LEVELInventor: Ezra B. Merriam,

` HIS Attorreg.

Patented May 25, 1937 Imotorino omom'r nv'rEnnnr'rEa Ezra B.V Merriam,Swarthmore, Pa., assig'nor General Electric Company, a corporation ofNew York Application January 2s, 193s, sei-iai No. cuss My inventionrelates to electric circuit interrupters, more particularly to circuitinterrupters of the liquid blast type wherein the are is subjected to asubstantially transverse or cross blast voi? arc extinguishing liquidduring a circuit opening operation, and has for its principal object theprovision of an improved circuit interruptor of the aforesaid type.

y My invention will be more fully set forth in the following descriptionreferring to the accompany drawing, and the features of novelty whichcharacterize my invention will be pointed out with particularity in theclaims annexed to and forming a part of this speciiication.

Referring to the drawing, Fig. i is an elevational view, partly insection, of the operative part of an electric circuit breaker lembodyingmy invention; Fig.2 is a similar view illustrating a modication of thearrangement shown by Fig. 1; Fig. 3 is an elevational view, partly insection, of a double-break type of circuit breaker; and Fig. 4 islikewise an elevational view, partly in section, of another form ofdouble-break circuit breaker embodying my invention.

In certain types of liquid blast circuit interrupters the arc formedupon opening of the circuit is drawn within a pressure conflning chamberadjacent to and generally transversely oi' a pressurerelief opening orport. The arc pressure generated within the chamber directs `a.turbulent blast of are extinguishing liquid through the relief port,tending to interrupt the arc at that point.- Where an appreciable bodyor head of arc extinguishing liquid, such as insulating oil for example,is directly in the path of the blast. it will be apparent thatacceleration of this mass of liquid tends to a certain degree to slow upthe application of the arc interrupting blast. l

In accordance with my invention, an appreciable part of the aforesaidbody of liquid is acA celerat-ed in a direction away from the liquidblast upon opening of the circuit by piston structure, or the equivalentthereof. coincident with d the circuit opening movement, the backpressure at the pressure relief or exhaust port is thereby appreciablydecreased so that the arc at that point is subjected to the eect of theliquid blast without appreciable delay.

50 Fig. 1 illustrates a simpleway of carrying out my invention in alow-voltage single-break oil circuit breaker. ln this case, the circuitbreaker casing i is provided with an insulating lining i and aninsulating partition 2 forming an upper low pressure or pressure 4reliefchamber 3 and a (ci. sou-15u) lower pressure confining or arc chamber I.A movable contact rod 5 extends through the partition 2 and engages atits lower end a iixed socket contact 6 which is mounted in the lowerwall of the switch casing. Upon opening the circuit, the rod contact 5is elevated for separating the contacts. The switch casing l contains asuitable arc extinguishing liquid,r such as circuit breaker oil, to thelevel indicated.

The pressure relief passage for the chamber 4 is formed in the presentinstance by insulating structure I forming an annular space or passage,the inner side oi which is providedvwith a circular port 8. This annularpassage is in communication at 8 with a pressure relief insulatingconduit-at lli formed along the side wall ofthe circuit breaker casing.As illustrated, the arc drawn between contacts 5 and 6 is centrally ofthe circular relief port 8 and transversely thereof, 'so that the arcpressure within the chamber I tends to expel oil through the arcradially into the relief port.

For the purpose of appreciably reducing the back pressure at the exhaustport 9 for facilitating the oil'blast, a piston Y il is mounted withinthe passage Hi which forms the cylinder thereof,

and is operatively connected to the movable rod contact 5 orswitchoperating mechanism so as to be raised when the rod contact israised. The particular arrangement for connecting the piston rod i2 tothe movable contact structure forms no part of the present invention andmay be as in Fig. 2 wherein the piston moves directly with the rodcontact, or as in Fig. 4 wherein the piston is connected through apivoted lever to the movable contact structure. In this latter case, ofcourse, the relative movement between the movable contact and piston maybe as desired.

The piston il upon opening of the circuit may initially move apredetermined, distance prior to actual separation of the contacts,thereby tending to set in motion, by suction, the oil towards y theexhaust passage 9V. Furthermore, if the speed of the piston H is greatlyincreased with respect to the contact opening movement, a partial vacuummay momentarily exist within the relief passage upon opening of thecircuit, therebyY greatly facilitating the oil blast from the chamber l.This increased speed of application of the oil blast is of considerableimportance in interrupting the arc within a few cycles at cornmecialfrequencies.

Fig'. 2 illustrates a modified form of Fig. l wherein the relief port issixnplied and provided with arc splitting insulating bames. In thisarrangement, the exhaust passage 9 is formed by a tubular extension I3of the insulating lining terminating adjacent the iixed contact S sothat the arc is drawn transversely of the passage 9.

An insulating baille I4 is suitably disposed within the passage 9transversely of the arc path so that the arc is broken up when driveninto the passage 9, the portions of the arc in the passage being actedupon by separate oil blasts.

The piston rod I2 is directly connected through a member I2v to themovable rod contact 5 for operating the piston in the manner abovedescribed upon opening of the circuit. However, as above pointed out,the connection between the piston II and the rod contact may be chosenso as best to anticipate the operating requirements of the breaker.

Fig. 3 illustrates a double-break oil circuit breaker comprising fixedcontacts I5 of the well known finger type construction and a movablebridging member I6 connected to a central lift rod I1 for moving thebridging member into and out of engagement with the contacts I5. The xedcontacts Il are mounted at the lower ends of the lead-in insulatingbushings I 8 which are suitably mounted in the cover structure (notshown). of the circuit breaker tank. The relatively movable contactstructure above described is immersed in an insulating liquid I9, suchas oil.

Enclosing the contact structure Within the main circuit breaker tank(not shown) is an insulating casing forming a pressure confining chamberand having pressure relief ports 2| opposite the breaks, respectively,formed between the iixed contacts Il and the bridging member I6. Thecasing 20 is provided with an upper insulating baille 22. preferablybelow the level of the oil I8, for directing the oil blast through theports 2I when arcing pressure is generated within the chamber. i

In this arrangement the'oil body in the path of the blast is acceleratedby means of `a piston 2l operatively connected to the lift rod I1 andoperable within an insulating cylinder 24. The cylinder 24 at its lowerend is provided with lateral exhaust openings 25 which are generally inalinement with the ports 2|. The piston 23 may have a resilientconnection with the rod I1 compricing a spring 2B and shoulder 21 forinitiating, if desired, movement of the contact structure prior tomovement of the oil piston. However, it will be apparent that thisarrangement may be reversed, if desired,.as in the previous case,

- depending upon the power of the operating mechanism available and therequirements ofthe breaker.

In operation, downward or opening movement of the bridging member I6 isaccompanied by movement of the piston 2l. causing a lateral flow of oilfrom the cylinder side ports 25 in the direction of the ports 2|. 'Ihearc pressure within the chamber, assisted by the accelerated body ofoil, is therefore more effective to expedite the oil blast andinterrupting arcing.

Fig. 4 illustrates an oil circuit breaker of the general type shown byFig. 3, wherein the oil body exteriorly of the relief ports isaccelerated and the back pressure at those ports appreciably reduced asin the case of Figs. 1 and 2. In this case. the circuit breaker tank'llcontains insulating oil I9 in which are immersed the fixed contacts I5and the movable bridging menibers Il. The lead-in insulating bushingsIl. as in v the prsviom instance, an suitably supported in the cover ofthe breaker tank. The bridging vmember is connected to the conventionallift rod I1 for opening and closing the circuit in the usual manner.Enclosing the contact structure, as in the previous case, is theinsulating casing 20 provided with the upper baiile 22 forming thepressure confining or arc chamber. The chamber is provided with lateralrelief ports 2| located opposite the two breaks formed upon opening ofthe circuit.

'I'he relief openings 2| communicate with upwardly extending cylindricalpassages 2B open- ,ing into the low pressureregion above `the baille 22.Operable within the cylindrical passages 28 are pistons II, the pistonrods I2 of which are connected, respectively, to the lift rod |1'through pivoted levers 29, respectively. 'Ihe levers 29 are pivotedwith respect to the circuit breaker struc` ture, as at 30, and areprovided with pin and slot connections at 3| and I2 with the pistons andlift rod, respectively. Further description of the operation of thecircuit breaker shown in Fig. 4 is believed to be unnecessary other thanto point out that the pressure generated within the arc chamber uponopening o'i' the circuit tends to cause va cross blast generallypredominating through one or the other of the relief ports 2l, thisblast being appreciably aided by the 1eduction of back pressure by thepiston operation at the aforesaid ports.

It should be understood that my invention is not limited to specicdetails of construction and arrangement thereof herein illustrated. andthat changes and modifications may occur to one skilled in the artwithout departing from the spirit of my invention. y

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. An electric circuit interrupter of the liquid blast type comprising acasing forming a pressure confining chamber, relatively movable contactsoperable within said chamber, said chamber containing an arcextinguishing liquid and provided with a pressure relief port, saidcontacts arranged to draw an arc within said chamber opposite andsubstantially transversely of said port so that arc pressure in saidchamber tends to extinguish the arc by liquid blast through said port,and a piston disposed exteriorly of said chamber operatively connectedwith respect to the movable contact for reducing by suction the backpressure to said liquid blast at the exhaust side of said port inaccordance with the circuit opening operation.

2. .An electric circuit interrupter of the liquid blast type comprisinga casing forming a pressure confining chamber, said chamber containingan arc extinguishing liquid, relatively movable contact structureoperable within said chamber including a pair of fixed contacts and amovable bridging contact arranged to form two breaks in series. saidchamber having a pressure relief port .substantially opposite each ofsaid breaks, and

piston structure disposed exteriorly of said chamber operativelyconnected with respect to said bridging contact for reducing thepressure in said chamber and accelerating liquid in the direction ofsaid ports and transversely of said breaks in accordance with thecircuit opening operation.

3. An electric circuit interrupter of the liquid blast type comprising acasing forming a pressure connning chamber, said chamber containing anarc extinguishing liquid, relatively movable contacts operable withinsaid chamber including a pair of 'xed contacts and a movable CFI and apiston operable exteriorly of each of said ports, and means operativelyconnecting said pistons with respect to said bridging contact forlowering the back pressure by suction at e'ach of said ports inaccordance with the circuit opening operation; l

' EZRA B. MERRIAM.

